Transistors and amplifier circuits based on III-V compound semiconductors (i.e., GaAs MESFET, GaAs pHEMT, In PHEMT, GaAs metamorphic HEMTs) are prone to high-frequency oscillation (known as Gunn oscillation) due the negative differential resistance of the velocity-field curve, which generates a traveling Gunn domain propagation, resulting in negative resistance in the drain output. Although the effect has been used for microwave/millimeter-wave generations, it is an undesirable phenomenon for the stable and efficient operation of power amplifiers. Under RF drives, this high-frequency oscillation can manifest itself as spurious signals at undesirable out-of-band frequencies. For high power microwave systems (i.e., for radar applications), the frequency spectrum needs to be spurious free at all frequencies and also near the carrier.
There is currently no effective way at the circuit level to suppress these undesirable oscillations in-band. For instance, conventional reflective filters operate out-of-band. There is desired a method of high-frequency suppression in a simple stabilization circuit monolithically integratable in a MMIC amplifier. Even though Gunn oscillation is cited as the main contributor to the negative drain output resistance, other types of high-frequency oscillations, such as IMPATT oscillation, are also desired to be effectively suppressed.